In an optical transmission module for optical interconnection, a light source element is required to operate in a wide temperature range from −40° C. to 80° C., for example. In order to meet such requirement, Patent document 1 discloses an optical transmission module provided with a temperature adjustment member such as a Peltier device or a heater so as to maintain a laser diode at a constant temperature.
However, since the above-mentioned optical transmission module is provided with the Peltier device or the heater, it is need to provide excessive electric power or part for driving the Peltier device or the heater, causing a problem that electric power saving, miniaturization of the module itself and cost reduction are difficult. Moreover, since the Peltier device and the heater are expensive, the optical transmission module equipped with the Peltier device or the heater is hard to be adopted as a consumer product.
In semiconductor lasers including a VCSEL (Vertical Cavity Surface Emitting LASER), a DBR (Distributed Bragg Reflector) laser and a DFB (Distributed Feedback) laser, a wavelength (λc) of an emitted laser beam is determined by a resonator and a reflecting mirror that is integrated (formed) in a semiconductor laser device. Thus, by matching a peak wavelength (λp) of a gain spectrum of an active layer with the wavelength λc, the semiconductor laser exhibits optimum characteristics (ex. high optical output and high power-light conversion efficiency). Conversely, as a difference between λp and λc becomes larger, the characteristics of the semiconductor laser are deteriorated.    [Patent document 1] Unexamined Patent Publication No. 2005-235867